There is a continuing demand for refinery products, including gasoline, distillates (e.g., diesel and jet fuels) and gaseous fuels. Because of this ongoing need for petroleum products, petroleum refiners are often forced to work with heavier, often hydrogen deficient, and high impurity feeds or simply wish to maximize the salable products from the raw materials. Also, there is a growing pressure to utilize every fraction of the crude oil including light refinery gases and residues, in the effort to optimize liquid fuel production.
U.S. Pat. No. 4,440,871 discloses a novel class of crystalline microporous silicoaluminophosphates. U.S. Pat. No. 4,310,440 discloses a novel class of crystalline aluminophosphates. These novel molecular sieves are disclosed as generally employable in catalytic cracking processes but no mention is made of employing such molecular sieves in conjunction with zeolitic aluminosilicate cracking catalysts.
In U.S. Ser. No. 772,858, now U.S. Pat. No. 4,734,185, filed concurrently with a parent of the present application and commonly assigned, a catalytic cracking process is disclosed using mixed catalysts comprising zeolitic aluminosilicates and at least one molecular sieve, including the molecular sieves of U.S. Pat. No. 4,440,871 characterized by an adsorption of isobutane of at least 2 percent by weight at a pressure of 500 torr and a temperature of 20.degree. C. Further, in U.S. Ser. No. 861,758, now U.S. Pat. No. 4,666,875, filed concurrently with a parent of the present application and commonly assigned, there is disclosed a process for the cracking of crude oil feedstock with a molecular sieve characterized by an adsorption of isobutane of at least 2 percent by weight at a pressure of 500 torr and a temperature of 20.degree. C.